Pneumatic pumps are known which can extract from the top of water tables lighter than water contaminants. For example see U.S. Pat. No. 5,004,405, issued Apr. 2, 1991, entitled "Pneumatically Powered Submersible Fluids Pump with Integrated controls." For the purpose of this disclosure this patent is incorporated by reference therein as if fully set forth.
In situations involving the relatively slow accumulation of surface contaminants, such pneumatic pumps are usually superior to pumps of the electric variety. For example, a pneumatic pump can intermittently stop and start easily; electric pumps which are called upon to intermittently stop and start frequently burn out or otherwise fail. Additionally, pneumatic pumps generally are superior in handling particulate matter; electric pumps frequently jam and burn out when particulate matter is present in the fluid contaminants.
In the closest prior art related to this invention, a pneumatic pump has a floating inlet which effectively floats with its inlet at its uppermost portion of the float. This unit floats at the interface between relatively dense underlying water and lighter overlying leachate. The specific gravity of the floating inlet is between the specific density of the lighter overlying leachate and the denser underlying water. The floating inlet floats well above the water surface with considerable "freeboard" when only water is present.
However, when this same float is immersed in the light overlying leachate, it sinks so that the floating inlet is well below the surface. Such a floating inlet is shown in U.S. Pat. No. 4,663,037.
Presuming that no pollutants are initially present, and lighter than water pollutants are being added to the surface of the water body, the freeboard of the float changes. The float gradually sinks in the lighter fluid until the inlet is submerged. The inlet then functions to collect the lighter than water fluid. When this inlet "sees" this lighter than water fluid, it conducts it via flexible tubing to the pump chamber, which is mounted below the float. Thus, the interior chamber of the pneumatic pump is flooded.
In U.S. Pat. No. 5,004,405, when the pump casing is flooded, a float interior of the pump chamber is buoyantly actuated, and a pumping cycle occurs to evacuate the flooded interior casing of the pump. This pumping cycle is typically continuously repeated so long as the interior chamber of the pneumatic pump is periodically flooded and then evacuated by pumping.
When the level of floating pollutant is reduced, the freeboard of the floating inlet increases, raising the inlet. This raising increases to the point where the pump inlet no longer "sees" fluid, and the interior chamber of the pump is no longer periodically flooded. As a direct consequence of this lack of periodic pump chamber flooding, pumping of the lighter fluid ceases.
This much is known and is closest prior art known to Applicant related to the invention that follows.